Method for manufacturing single-pole only usable magnet

Abstract

Provided is a method of manufacturing a magnet capable of using only a single pole, whereby a combination force between a permanent (or referred to as a magnet) and a yoke (or referred to as a shielding metal) can be improved without performing a manual bonding work therebetween and then the efficiency of subsequent processes, such as polishing and plating, after combination and completeness of a product can be improved.

Claims

1. A method of manufacturing a magnet capable of using only a single pole, the method comprising: (a) forming a green compact having an oriented powder by magnetically pressing an alloy powder for manufacturing a magnet; (b) placing an iron-based metal powder for manufacturing a shielding metal so that at least one surface of the green compact is exposed and the remaining surfaces of the green compact are surrounded; (c) forming a compression molded body by mechanically pressing a resultant structure of (b); and (d) forming a sintered body by sintering the compression molded body.

2. The method of claim 1, wherein (b) comprises: (b-1) placing the green compact in a center of a bottom of a predetermined mold; and (b-2) putting the iron-based metal powder into the predetermined mold in a state of (b-1).

3. The method of claim 1, further comprising (e) performing polishing, plating and magnetization on the sintered body.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A through 1F are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to an embodiment of the present invention;

(2) FIGS. 2A through 2G are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to another embodiment of the present invention;

(3) FIGS. 3A through 3G are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to another embodiment of the present invention;

(4) FIGS. 4A through 4I are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to another embodiment of the present invention; and

(5) FIGS. 5A through 5C are views of the flow of a magnetic field of a general permanent magnet and the flow of a magnetic field of a permanent magnet having a yoke combined thereto, respectively.

BEST MODE FOR CARRYING OUT THE INVENTION

(6) The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

(7) A method of manufacturing a magnet capable of using only a single pole according to the present invention may include: a first process of providing an alloy powder for manufacturing a magnet, a first alloy powder green compact having an oriented powder by magnetically pressing the alloy powder for manufacturing a magnet, or a second alloy powder green compact formed by mechanically pressing the first alloy powder green compact; a second process of providing an incompletely-sintered body formed by incompletely sintering an iron-related metal powder for manufacturing a shielding metal or a metal powder green compact of the iron-related metal powder for manufacturing a shielding metal; a third process of placing a resultant structure of the first process and a resultant structure of the second process so that at least one surface of the resultant structure of the first process is exposed and the remaining surfaces thereof are surrounded by the resultant structure of the second process; and a fourth process of forming a sintered body by sintering a resultant structure of the third process, and may further include: a fifth process of performing polishing, plating, and magnetization on the sintered body as a resultant structure of the fourth process.

(8) Subsequently, specific example embodiments of the present invention will be described.

(9) FIGS. 1A through 1F are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to an embodiment of the present invention.

(10) First, as illustrated in FIG. 1A, an alloy powder 111a for manufacturing a magnet is put into a first mold 110, and as illustrated in FIG. 1B, a magnetic field is applied to the alloy powder 111a, and the alloy powder 111a is pressed, i.e., magnetically pressed, thereby manufacturing an alloy powder green compact 111b having an oriented powder.

(11) The alloy powder 111a for manufacturing a magnet may include a fine powder of a neodymium (Nd)-iron (Fe)-boron (B)-based magnet alloy manufactured by preparing a bulk of the Nd—Fe—B-based magnet alloy using a strip cast method, for example, and grinding the bulk into a jet mill in an inert gas.

(12) Next, as illustrated in FIG. 1C, an iron-related metal powder 121a for manufacturing a shielding metal is put into a second mold 120 in a state in which the center of the alloy powder green compact 111b is fitted to the center of a bottom surface of the second metal 120, and when the second mold 120 is removed, at least one surface (a bottom surface in the drawing) of the alloy powder green compact 111b is exposed, and the remaining surfaces (side surfaces and a top surface in the drawing) of the alloy powder green compact 111b are surrounded by the iron-related metal powder 121a for manufacturing the shielding metal.

(13) Next, as illustrated in FIG. 1D, a compression molded body 130 including the alloy powder green compact 111b for manufacturing a magnet and an iron-related metal powder green compact 121b for manufacturing a shielding metal is manufactured by mechanically pressing the resultant structure of FIG. 1C. In the current embodiment, the compression molded body 130 has a shape in which, when the second mold 120 is removed, one surface of the alloy powder green compact 111b for manufacturing a magnet is exposed and the remaining surfaces thereof are surrounded by the metal powder green compact 121b.

(14) Next, as illustrated in FIG. 1E, the compression molded body 130 as the resultant structure of FIG. 1D is sintered, thereby manufacturing a sintered body 140 of the compression molded body 130 in which a sintered body 111c of the alloy powder green compact 111b for manufacturing a magnet and a sintered body 121c of the metal powder green compact 121b for manufacturing a shielding metal are integrally sintered.

(15) For example, after a compression process including magnetic pressing and mechanical pressing is performed, a sintering and heat treatment process is performed on a base material having a relative density of about 50% to about 60% at a high temperature so that the relative density of the base material is able to be close to 95% to 100%. When the relative density of the base material increases, a residual magnetic flux density Br and a mechanical strength of the base material can be increased, and sintering may be performed on the base material about 1,300° C., and three-step (1,100° C.-950° C.-500° C.) heat treatment can be performed on the base material.

(16) Last, as illustrated in FIG. 1F, polishing, plating, and magnetization processes are sequentially performed on a sintered body 140 as the resultant structure of FIG. 1E so that a shielding magnet 150 including a permanent magnet 111d having one exposed surface and a shielding metal 121d that surrounds the remaining surfaces of the permanent magnet 111d is completed. In the current embodiment, the permanent magnet 111d corresponds to the sintered body 111c of the alloy powder green compact 111b for manufacturing a magnet, and the above-described shielding metal 121d corresponds to the sintered body 121c of the metal powder green compact 121b for manufacturing a shielding magnet.

(17) For example, a barrel polishing method may be used in the polishing process as a process of assigning R-values to a surface and edges of the product before a surface treatment process is performed. An electroplating and electroless plating method may be used as the plating process as a process of preventing oxidation and corrosion of the product, and a nickel (Ni)-copper (Cu)—Ni multilayer plating method may be performed. The thickness of a film may be 10 to 25 μm in case of Ni and 5 to 10 μm in case of zinc (Zn). The magnetization process is a magnetization work of aligning magnetic spins in a predetermined direction by applying an external magnetic field to the product, and a magnetic-field strength of 1.5 to 3 times of coercivity of the product is required to be applied to the product so that saturation magnetization can be implemented (a work needs to be performed at 1500 volt/2,000 μF or higher.).

(18) In the current embodiment, external shapes of the permanent magnet 111d and the shielding metal 121d may be changed according to the shapes of the first mold 110 and the second mold 120.

(19) FIGS. 2A through 2G are views of illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to another embodiment of the present invention.

(20) First, as illustrated in FIG. 2A, an iron-related metal powder 211a for manufacturing a shielding metal is put into the first mold 210, and as illustrated in FIG. 2B, the iron-related metal powder 211a is mechanically pressed so that a metal powder green compact 211b having a groove with a predetermined size in the center of one surface thereof can be formed.

(21) Subsequently, as illustrated in FIG. 2C, the metal powder green compact 211b is sintered (is not completely sintered but is incompletely sintered) so that an incompletely-sintered body 211c having a groove can be formed. Incomplete sintering may be performed by adjusting relative sintering temperature and time compared to complete sintering.

(22) As illustrated in FIG. 2D, the alloy powder for manufacturing a magnet in the second mold 220 is magnetically pressed so that an alloy powder green compact 221a having an oriented powder can be manufactured to have a shape corresponding to the groove of the incompletely-sintered body 211c. A manufacturing method thereof may be the same as the processes of FIGS. 1A and 1B.

(23) Subsequently, as illustrated in FIG. 2E, after the alloy powder green compact 221a of FIG. 2D is inserted into the groove formed in the incompletely-sintered body 211c of FIG. 2C using press fitting, as illustrated in FIG. 2F, the resultant structure of FIG. 2E is completely sintered, thereby manufacturing a sintered body 230 in which a completely-sintered body 221b of the alloy powder green compact 221a for manufacturing a magnet and a completely-sintered body 211d of the incompletely-sintered body 211c of the iron-related metal powder green compact 211b for manufacturing a shielding metal are integrally sintered. Complete sintering may be performed by adjusting relative sintering temperature and time compared to incomplete sintering. The resultant structure of FIG. 2E is pressed and then can be completely sintered in FIG. 2F.

(24) Last, as illustrated in FIG. 2G, polishing, plating, and magnetization processes may be sequentially performed on the (completely-) sintered body 230 as the resultant structure of FIG. 2F so that a shielding magnet 240 including the permanent magnet 221c having one exposed surface and a shielding metal 211e that surrounds the remaining surfaces of the permanent magnet 221c can be manufactured. In the current embodiment, the permanent magnet 221 corresponds to the completely-sintered boy 221b of the alloy powder green compact 221a for manufacturing a magnet, and the shielding metal 211e corresponds to the completely-sintered body 211d of the incompletely-sintered body 211c of the iron-related metal powder green compact 211b for manufacturing the shielding metal.

(25) For example, a barrel polishing method may be used in the polishing process as a process of assigning R-values to a surface and edges of the product before a surface treatment process is performed. An electroplating and electroless plating method may be used as the plating process as a process of preventing oxidation and corrosion of the product, and a Ni—Cu—Ni multilayer plating method may be performed. The thickness of a film may be 10 to 25 μm in case of Ni and 5 to 10 μm in case of zinc (Zn). The magnetization process is a magnetization work of aligning magnetic spins in a predetermined direction by applying an external magnetic field to the product, and a magnetic-field strength of 1.5 to 3 times of coercivity of the product is required to be applied to the product so that saturation magnetization can be implemented (a work needs to be performed at 1500 volt/2,000 μF or higher.).

(26) In order to adjust surface flatness after the processes of FIG. 2F are performed, a mechanical pressing process may be performed so that a planarization process of the surface of the completely-sintered body 230 can be further performed.

(27) In the current embodiment, external shapes of the shielding metal 211e and the permanent magnet 221c may be changed according to the shapes of the first metal 210 and the second metal 220.

(28) FIGS. 3A through 3G are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to another embodiment of the present invention.

(29) First, as illustrated in FIG. 3A, an iron-related metal powder 311a for manufacturing a shielding metal is put into a first mold 310, and as illustrated in FIG. 3B, the iron-related metal powder 311a is mechanically pressed so that a metal powder green compact 311b having a groove with a predetermined size in the center of one surface thereof can be formed.

(30) Subsequently, as illustrated in FIG. 3C, the metal powder green compact 311b is sintered (is not completely sintered but is incompletely sintered), thereby forming an incompletely-sintered body 311c having a groove. Incomplete sintering may be performed by adjusting relative sintering temperature and time compared to complete sintering.

(31) Subsequently, as illustrated in FIG. 3D, an alloy powder 321a for manufacturing a magnet is put into a groove formed in the incompletely-sintered body 311c as the resultant structure of FIG. 3C, and as illustrated in FIG. 3E, the alloy powder 321a for manufacturing a magnet is magnetically pressed so that an alloy powder green compact 321b having an oriented powder can be formed.

(32) Subsequently, as illustrated in FIG. 3F, the resultant structure of FIGS. 3D and 3E is completely sintered so that a (completely-) sintered body 330 in which a completely-sintered body 321c of the alloy powder green compact 321b for manufacturing a magnet and a completely-sintered body 311d of an incompletely-sintered body 311c of the iron-related metal power green compact 311b for manufacturing a shielding metal are integrally sintered, can be manufactured. Complete sintering may be performed by adjusting relative sintering temperature and time compared to incomplete sintering. The resultant structure of FIGS. 3D and 3E is mechanically pressed and then can be completely sintered in FIG. 3F.

(33) Last, as illustrated in FIG. 3G, polishing, plating, and magnetization processes are sequentially performed on the sintered body 330 as the resultant structure of FIG. 3F so that a shielding magnet 340 including a permanent magnet 321c having one exposed surface and a shielding metal 311e that surrounds the remaining surfaces of the permanent magnet 321c is completed. In the current embodiment, the permanent magnet 321c corresponds to the completely-sintered body 321c of the alloy powder green compact 321b for manufacturing a magnet, and the shielding metal 311e corresponds to the completely-sintered body 311d of the incompletely-sintered body 311c of the iron-related metal powder green compact 311b for manufacturing a shielding magnet.

(34) For example, a barrel polishing method may be used in the polishing process as a process of assigning R-values to a surface and edges of the product before a surface treatment process is performed. An electroplating and electroless plating method may be used as the plating process as a process of preventing oxidation and corrosion of the product, and a nickel (Ni)-copper (Cu)—Ni multilayer plating method may be performed. The thickness of a film may be 10 to 25 μm in case of Ni and 5 to 10 μm in case of zinc (Zn). The magnetization process is a magnetization work of aligning magnetic spins in a predetermined direction by applying an external magnetic field to the product, and a magnetic-field strength of 1.5 to 3 times of coercivity of the product is required to be applied to the product so that saturation magnetization can be implemented (a work needs to be performed at 1500 volt/2,000 μF or higher.).

(35) In order to adjust surface flatness after the processes of FIG. 3F are performed, a mechanical pressing process may be performed so that a planarization process of the surface of the completely-sintered body 330 can be further performed.

(36) In the current embodiment, external shapes of the shielding magnet 211e may be changed according to the shapes of the first mold 310, and the iron-related metal powder 311a may be mechanically pressed in the process of FIG. 3B so that the external shapes of the permanent magnet 221c can be changed according to the shape of a groove formed in the center of one surface of the metal powder green compact 311b.

(37) FIGS. 4A through 4I are views illustrating detailed processes of a method of manufacturing a magnet capable of using only a single pole according to another embodiment of the present invention.

(38) First, as illustrated in FIG. 4A, an iron-related metal powder 411a for manufacturing a shielding metal is put into a first mold 410, and as illustrated in FIG. 4B, the iron-related metal powder 411a is mechanically pressed so that a metal powder green compact 411b having a groove with a predetermined size in the center of one surface thereof can be formed.

(39) Subsequently, as illustrated in FIG. 4C, the metal powder green compact 411b is sintered (is not completely sintered but is incompletely sintered) so that an incompletely-sintered body 411c having a groove can be formed. Incomplete sintering may be performed by adjusting relative sintering temperature and time compared to incomplete sintering, and the incompletely-sintered body has a predetermined tension.

(40) As illustrated in FIG. 4D, an alloy powder 421a for manufacturing a magnet is put into a second mold 430, and as illustrated in FIG. 4E, the alloy powder 421a is magnetically pressed so that a first alloy powder green compact 421b having an oriented powder can be formed. Then, as illustrated in FIG. 4F, the first alloy powder green compact 421b is mechanically pressed so that a second alloy powder green compact 421c can be manufactured. The second alloy powder green compact 421c has a shape corresponding to the groove of the incompletely-sintered body 411c.

(41) Subsequently, as illustrated in FIG. 4G, after the second alloy powder green compact 421c of FIG. 4F is inserted into the groove formed in the incompletely-sintered body 411c of FIG. 4c and then, as illustrated in FIG. 4H, the resultant structure of FIG. 4G is completely sintered so that a (completely-) sintered body 430 in which a completely-sintered body 421d of the alloy powder green compact 421c for manufacturing a magnet and a completely-sintered body 411d of the incompletely-sintered body 411c of the iron-related metal powder green compact 411b for manufacturing a shielding metal are integrally sintered, can be manufactured. Incomplete sintering may be performed by adjusting relative sintering temperature and time compared to incomplete sintering.

(42) Last, as illustrated in FIG. 4I, polishing, plating, and magnetization processes are sequentially performed on the (completely-) sintered body 430 as the resultant structure of FIG. 4H so that a shielding metal 440 including a permanent magnet 421e having one exposed surface and a shielding metal 411e that surrounds the remaining surfaces of the permanent magnet 421e can be manufactured. In the current embodiment, the permanent magnet 421e corresponds to the completely-sintered body 421d of the alloy powder green compact 421c for manufacturing a magnet, and the shielding metal 411e corresponds to the completely-sintered body 411d of the incompletely-sintered body 411c of the iron-related metal powder green compact 411b for manufacturing a shielding metal.

(43) For example, a barrel polishing method may be used in the polishing process as a process of assigning R-values to a surface and edges of the product before a surface treatment process is performed. An electroplating and electroless plating method may be used as the plating process as a process of preventing oxidation and corrosion of the product, and a Ni—Cu—Ni multilayer plating method may be performed. The thickness of a film may be 10 to 25 μm in case of Ni and 5 to 10 μm in case of zinc (Zn). The magnetization process is a magnetization work of aligning magnetic spins in a predetermined direction by applying an external magnetic field to the product, and a magnetic-field strength of 1.5 to 3 times of coercivity of the product is required to be applied to the product so that saturation magnetization can be implemented (a work needs to be performed at 1500 volt/2,000 μF or higher.).

(44) In order to adjust surface flatness after the processes of FIG. 4H are performed, a mechanical pressing process may be performed so that a planarization process of the surface of the completely-sintered body 230 can be further performed.

(45) In the current embodiment, external shapes of the shielding metal 411e and the permanent magnet 421e may be changed according to the shapes of the first mold 410 and the second mold 420.

(46) FIGS. 5A through 5C are views of the flow of a magnetic field of a general permanent magnet and the flow of a magnetic field of a permanent magnet having a yoke (shielding metal) combined thereto, respectively.

(47) In the permanent magnet, a magnetic line is formed in a fully-opened state, as illustrated in FIG. 5A. However, when the permanent magnet is sealed by a metal yoke having high permeability, the magnetic line as illustrated in FIGS. 5B and 5C appears in the permanent magnet according to the shape of the yoke.

(48) That is, in the magnetic field of the permanent magnet, an attractive force and a repulsive force are differently generated according to a metal, and degrees thereof varies according to permeability of the metal. When a metal having high permeability is close to the permanent magnet, the flow of the magnetic field is changed. Also, when the metal is close to the permanent magnet after the shape and the thickness of the metal are properly designed, directivity of the magnetic field through induction of the flow of the magnetic field can be changed.

(49) Thus, the yoke can be integrally combined with the permanent magnet by changing the material, thickness and shape of the yoke according to the degree of reinforcement of a required magnetic force and the degree of shielding. Thus, a reinforcement ratio and a shielding ratio of the shielding magnet can be changed.

(50) Thus, like in the above-described embodiment of the present invention, a shielding magnet 150, 240, 340 or 440 including a permanent magnet 111d, 221c, 321d, or 421e having one exposed surface and the remaining surfaces surrounded by a shielding metal 121d, 211e, 311e, or 411e as a yoke may generate the magnetic line illustrated in FIG. 5B and thus may be used as a magnet capable of using only a single pole.

(51) As described above, according to the present invention, because combination of an alloy powder for manufacturing a magnet that constitutes a permanent magnet (magnet) and a yoke (a shielding metal) and an iron-related metal powder for manufacturing a shielding metal is performed during processes (for example, compression, sintering, etc.) required to manufacture a magnet, a combination force therebetween can be greatly increased without additionally performing an existing manual bonding work, and a shielding magnet, i.e., a magnet capable of using only a single pole, as a final base material is formed as one sintered body so that the efficiency of subsequent processes such as polishing, plating and magnetization after sintering and the completeness of the product can be improved.

(52) Thus, compared to a conventional shielding magnet in which a permanent magnet and a yoke are bonded to each other using an additional manual work and are combined with (joined to) each other, an adhesion can be greatly improved, and labor costs and a working time can be greatly reduced, the unit price of the product can be reduced, and the efficiency of a manufacturing process and the completeness of the product can be improved.

(53) While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.